Methods are known for desalting and dehydrating crude oils having initial boiling temperatures above 150.degree. C. to which a demulsifier, is added, followed by desalting by single stage washing. Then the crude oil containing about 20% water, is dehydrated by stripping with a hot gas at about 250.degree. C. The resulting crude oil is then used as a thermal agent in preheating the untreated crude oil; finally the desalted and dehydrated crude oil is led to storage.
These methods have several disadvantages they cannot be used for crudes having a high content of light fractions and salt; they require large amounts of demulsifier, which is removed together with the residual water; and the thermal energy consumption is relatively high.
The apparatus used for desalting and dehydration can comprise tanks in which washing, heating, settling and desalting of the crude occur in a single stage, heaters for gas heating, stripping columns, and pumps for circulating the crude and compressors for gas recirculation.
The disadvantage of such apparatus is that the tank volumes being relatively high, the thermal energy recovery efficiency is rather low.